A novel hybrid excitation flux switching synchronous machine for a high-speed hybrid electric vehicle applications

Hybrid excitation machines (HEMs) that consist of permanent magnet (PM) and field excitation coil (FEC) as their main flux sources has several attractive features compared to interior permanent magnet synchronous machines (IPMSM) conventionally employed in hybrid electric vehicles (HEVs). Among various types of HEM, the machine with both permanent magnet and field excitation coil located on the stator has the advantage of robust rotor structure similar as switch reluctance machine (SRM). In addition, the variable flux control capabilities from field excitation coil make this machine becoming more attractive to be applied for high-speed motor drive systems, coupled with reduction gear. This HEM can be categorized as hybrid excitation flux switching synchronous machine (HEFSSM). In this paper, a novel 12Slot-10Pole HEFSSM where the field excitation coil is wounded in radial direction in the stator is proposed for traction drives in HEVs. The design target of the proposed machine is a maximum torque of 210Nm with reduction gear ratio of 4:1, a maximum power of 123kW, a maximum power density more than 3.5kW/kg, and a maximum speed of 20,000r/min with similar restrictions and specifications in IPMSM used for LEXUS RX400h. The deterministic design optimization method based on 2D-FEA is used to treat design parameters defined in rotor, armature coil slot and field excitation coil slot until the target performances are achieved, under maximum current density condition for both armature coil and field excitation coil. The final results show that the final design HEFSSM is able to keep the same torque density in existing IPMSM installed on a commercial SUV-HEV.